Charlize Theron: Sean Penn romance makes life better

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While the loved-up pair have been packing on the PDA at charity galas and looking happy together on the red carpet, both Oscar-winning stars have remained pretty hush-hush about their relationship... until now.

The South African-born beauty revealed some details about her blossoming romance with Penn to Jonathan Van Meter for the June issue of Vogue.

The 38-year-old star admitted she was unsure of "how you have a healthy relationship with the whole world knowing about it."

However, Theron did open up about Penn, saying, "What I will say is, I was single for a really long time. I was enjoying mommyhood. You just naturally become kind of selfish about your time, and all of it is dedicated to this little thing, whether he needs it or not."

So how did the Monster actress know Penn was going to be the right person romantically for her?

"I know so well what I want to fit in my life," she explained. "And the simple answer to that is: Unless he can make my life better? My life is really pretty f***ing good."

"What I guess I am trying to say is: A friend kind of stepped into that role, and I really didn't see it coming," Theron admitted. "Sean and I have known each other for 18 years. We were just really good friends. And it's been slow going because you are aware that you could screw that up and lose it."

So how do you determine if a romance is worth risking a long-term friendship over?

"We had to think about it," Theron confessed. "But at the end of the day, it was somewhat effortless. It just kind of naturally happened, and before I knew it, I was in something that was making my life better — the people who really love me can see the effect it has had on me."